PROCESS FOR THE PREPARATION OF A COMPOSITION COMPRISING LONG CHAIN POLYUNSATURATED FATTY ACIDS

Abstract

Process for the preparation of a composition comprising long chain polyunsaturated fatty acids of the &#969;-3 and/or &#969;-6 series and/or the pharmaceutically and/or dietetically acceptable derivatives thereof selected from C1-C3 alkyl esters and/or the salts thereof with an inorganic or organic base with an assay higher than 50% by weight, wherein the starting polyunsaturated compounds are first concentrated up to a gaschromatographic purity corresponding to the assay required for the final composition and then dissolved in aprotic and/or apolar and/or poorly polar solvents before being purified by contact with silicon derivatives.

Full Text

PROCESS FOR THE PREPARATION OF A COMPOSITION COMPRISING
UNSATURATED COMPOUNDS
******
The present invention relates to a process for the preparation of a
composition comprising unsaturated compounds, in particular
polyunsaturated compounds, which comprises concentrating and
purifying the compounds.
It is known that unsaturated compounds, in particular the
polyunsaturated ones, are scarcely stable and easily deteriorated,
amongst others, by atmospheric agents, because of their own reactivity
and oxidability on double bonds, with subsequent production of polar
oxidation by-products and induction of polymerization.
Among the most instable unsaturated compounds comprised in the
composition obtained by the process of the invention, the natural and
non-natural oils, of both animal and vegetable origin as well as the
products of their chemical modification, like fish and seed oils
(triglycerides), the fatty acids and salts thereof obtained by hydrolysis, the
alkyl esters thereof obtained by synthesis or by transesterification, as well
as any of the derivatives thereof, can be mentioned.
In particular, the family of the compounds deriving from the
polyunsaturated fatty acids of the ω-3 series, such as, for instance, the α-
linolenic acid (ALA, C18:4 Ω-3, all cis), the eicosapentaenoic acid (EPA,
C20:5 Ω-3, all cis), and the docosahexaenoic acid (DHA, C22:6 Ω-3, all
cis), and from the polyunsaturated fatty acids of the ω-6 series, as well as
the pharmaceutically and dietetically acceptable derivatives thereof,
typically the salts and the C1-C3 alkyl esters thereof, can be mentioned.
Among said derivatives, the EPA ethyl ester and/or DHA ethyl ester,
alone or in mixture, or even in the presence of other ethyl esters of
quantitatively minor ω-3 series compounds, are of particular interest for
their use in the pharmaceutical field and as dietetic integrators.
The natural oils containing fatty acids in the form of glycerides are
usually submitted to standard treatments, as extraction, whitening,
deodorization, etc. The polyunsaturated compounds, as -for instance- the
above mentioned acids, being in mixture with high quantities of saturated

and mono-unsaturated components, arc usually isolated from glycerides
through hydrolysis or through transesterification and concentrated, for
instance by complexing the less unsaturated constituents with urea or by
other techniques, chemically modified to derivatives, if requested, and
then purified by distillation: however, all these steps damage heavily and
at the same time the polyunsaturated compound structure and lead to
forming high quantities of by-products with polar structure, which sum
themselves to the other preexistent impurities of natural oils or deriving
by the environmental polluting agents.
Among the instability factors, the atmospheric agents, essentially air
oxygen, as well as other oxidizing agents, oxidation catalysts, such as
copper and iron; sunlight exposure, hydrolytic agents and the like, can be
mentioned. Actually, also many chemical and physical agents, used in the
extraction steps of such unsaturated compounds from the natural
sources, as well as in the concentration steps and also in the purification
steps, can induce some degradation, so forming oxidation and
polymerization products. The effect of heating is also particularly
dangerous, so that also distillation -while permitting to discard the lower
boiling and higher boiling fractions from the oily matrix- induces by itself
a high degradation and forming of polymeric residues.
To partially limit such problems, at least in the final steps of the
production, molecular distillation is carried out, which is however
disadvantageous because of the plant and managing costs and of its
limited productivity. In the commercializing steps, storage in tightly
closed containers, protected from air and from sunlight, and under inert
gas is also adopted. The addition of antioxidants, like for instance
tocoferol is also usual.
The polar degradation derivatives are therefore present in the raw
materials or are formed in the extraction, concentration, purification
steps, as well as during any further step of either chemical or generic
manipulation. Among such polar degradation derivatives, most of them
having a complex and not completely elucidated structure, we can
mention the hydroxy- derivatives on the double bond, the epoxides and
peroxides, the last ones being deemed as potentially dangerous to health,

in view of their atherogenic and mutagenic activities (see f . i. Carroll KK,
Cancer Res. 1975; 35, 3374). Other process by-products are represented
by several oligomers and polymers with complex structures, deriving by
said double bond oxidation products through different mechanisms
involving intermolecular reactions. These polymerization products
represent the most abundant by-products and may reach amounts of 20-
30% or more.
Completely foreign impurities, of environmental origin, but always
present, particularly in fish oils and in all their transformation derivatives,
are represented by several toxins, as aflatoxin, hydrocarbons as
benzopyrene, pesticides as DDT, industrial agents as PCB and dioxin
(McEwen FL, Stephenson GR, The use and significance of pesticides in
the environment, Chapter 15. New York, Wiley 1979, 260-348), metallic
ions and metallorganic compounds as mercury and methylmercury
(Bolger PM, Schwetz BA, N Engl J Med 2002; 347, 1735), and many other
marine pollutants, all clearly noxious to health if ingested as food and /or
as drug. Other polar derivatives can be constituted by acids deriving from
hydrolysis of triglycerides or esters, etc.
To avoid the presence of many foreign substances and by-products in
vegetable and animal oils, traditionally used for alimentary purpose, the
chemical practice obliged for decades the control of defined parameters as
acidity index, peroxide index, iodine index, the search of heavy metals, as
mercury and lead and of pesticides, anisidine index, etc.
After the recent development of the derivatives of polyunsaturated
fatty acids, more easily oxidized and degraded, as pharmaceutical
products, it is now deemed appropriate to carry out a chromatographic
analysis determining not only the so-called "gaschromatographic purity",
which is indeed an apparent assay (percent ratio of the peak area of each
component to the total area of the chromatogram), but even its "true
assay" (absolute assay) determined against a pure standard: also the
absolute area of the test derivative peak is thus controlled, this technique
guaranteeing, in other words, that substantial impurity quantities are not
retained in the chromatographic column escaping the instrumental
control.

The recent European Pharmacopoeia 2000 (E. P. 2000), in its
monograph "Omega-3 acid ethyl esters", a mixture of ethyl esters of
omega-3 polyunsaturated acids, typically represented by EPA and DHA,
prescribes the direct control of the oxidation and polymerization by-
products (defined "oligomers", as a whole, which are not detectable by
gaschromatographic route), by means of a specific exclusion
chromatography in liquid phase (gel permeation GPC, well known in the
art). We will refer hereafter to such specific chromatographic procedures,
carried out as described in E. P. 2000.
Coming back to the unsaturated substances object of the process of
the invention, just a few of them can be found and extracted from natural
products already in high concentration, as oleic acid (monounsaturated)
from olive oil; many others are found in low to medium concentration, as
arachidonic acid (polyunsaturated, ω-6) in the borage oil, and as EPA and
DHA (polyunsaturated, ω-3) in fish oil, where they can be present till to a
maximum of 10-20%, as it is easily documented by literature.
The processing of extracted oils (triglycerides) is usually carried out
by hydrolysis to acids or by transesterification to esters; acids and esters
can be used as such or undergone to chemical modification according to
methods known in the art, to give a wide range of derivatives. Frequently,
more often during the first steps of the processing, the lower concentrated
polyunsaturated substances are partially concentrated f. i. by complexing
them with urea and then fractioning/removing the saturated and
monounsaturated components, by means of procedures already well-
known to the expert by many decades (see Swern D, Techniques of
Separation - Urea Mixtures, in "Fatty Acids", part 3, Ed. KS Markley,
Interscience, New York, 1963; pages 2309-2358), or even by means of
distillation.
Further concentration and final purification are usually carried out
by under-vacuum distillation which results to be complicated by severe
pyrolytic effects on the unstable unsaturated structures, or by molecular
distillation, which limits indeed and yet does not eliminate the thermic
degradation and, however, implies expensive plant and managing plant
costs and limited productive capacity.

Fractioning with urea and molecular distillation are the techniques,
pointed out in the above mentioned monograph, for compositions based
on EPA ethyl ester, DHA ethyl ester and other minor components of the
ω-3 series. Other occasionally used purification techniques imply the
extraction and purification with supercritical fluids, Craig counter current
chromatography, and high pressure liquid chromatography (HPLC).
The most relevant patent literature describes what has already been
mentioned, as distillation is the final and essential phase to concentration
and/or to purification in almost all cases.
For example, US 4377526 describes a process for the purification of
EPA and the esters thereof, involving the treatment with urea, followed by
a fractioned distillation. Percentages of EPA higher than 70% are obtained,
while DHA is present at 3-5%.
US 4554107 and US 4623488 describe a method based on the
technique of molecular distillation: fish oil, enriched in EPA and DHA,
with a rather low yield (30%) because of the drastic experimental
conditions, is obtained.
US 5130061 relates to a process to obtain EPA and DHA as ethyl
esters from crude fish oils, through transesterification with ethanol and
acid catalyst (H2SO4), chromatography on silica gel and molecular
distillation. Distillation is the essential step of the process, to remove EPA
and DHA ethyl esters impurities (concentration 35-40%, Example 3), and
to increase their concentration from 40-50% to 80-90% (Examples 4-8)
and DHA ethyl ester concentration to 90-96% (Examples 9-10).
Also EP-B-0409903 claims a process, through which oils of animal
and/or vegetable origin are undergone to alkaline hydrolysis and the
obtained acids are undergone to one or more steps of molecular
distillation. The patent points out some prior art processes, based on the
use of urea for the precipitation and selective elimination of less
unsaturated acids (WO 87/03899, JP 57-187397) or on the extraction
with supercritical fluids (JP 60-214757, JP 60-115698).
Further processes of chromatographic type are reported in the
following patents: JP 61-291540 uses an absorbent resin composed of a
non-polar porous polymer (styrene-divinylbenzene copolymer) and an

eluent, containing a hydrophilic polar solvent, preferably methanol,
suitably modified, to fraction the required polyunsaturated acid or its
ester.
JP 61-037752 uses a chromatographic process on a co-polymer,
containing monovinyl and polyvinyl aromatic monomers.
JP 58-109444 uses chromatographic columns, composed of a carrier
made of silica gel or synthetic polymers (preferably substituted by an
octadecyl radical), suitable for a reverse-phase repartition
chromatography, and polar eluents, including water, alcohols and other
solvents.
Finally, IT 1235879 claims a process, to obtain a particular
composition of EPA, DHA and other minor components of ω-3 series,
already present in natural fish oil, according to which the known
techniques of transesterification, concentration -preferably through a
treatment with urea- and molecular distillation are used in free order.
In view of the above prior art, it is believed that the real absolute
purity of the obtained products has never been taken into consideration,
with the exception of some occasional gaschromatographic data.
For this reason, we believe it is reasonable to think the authors were
referring to the simple or apparent gaschromatographic purity, so that -
presumably unaware- such processes led to a more far away quality than
the supposed one and to products highly contaminated by impurities and
polluting agents, and above all, by the already mentioned polar products
of degradation (oxidation/polymerization), which are not detectable
through gaschromatography, but only through liquid chromatography of
exclusion, briefly reported as "oligomers", according to E.P. 2000.
It has been now surprisingly found a process for the preparation of a
composition comprising unsaturated compounds with a assay higher
than 50% by weight -considered as the absolute assay, according to what
above illustrated-, wherein the starting unsaturated compounds are first
concentrated up to a gaschromatographic purity corresponding to the
assay required for the final unsaturated compounds and then purified by
contact with silicon and/or aluminium derivatives.
The process of the invention allows to get purified unsaturated

compounds by simply contacting them with silicon and/ or aluminium
derivatives, without the need of any further manipulation to increase
neither the concentration nor the purity of the unsaturated compounds,
likely because of the high binding capacity of the polar by-products of the
process, of the products of polymerization and of the other
impurities/pollutants with the above mentioned silicon and/or
aluminium derivatives.
The unsaturated compounds are preferably polyunsaturated
compounds; it is also preferred that the composition has a content of
oligomeric impurities lower than 30% by weight, in particular lower than
15% by weight.
In the present specification, the expression 'oligomeric impurities' is
meant to comprise also other foreign impurities not detectable through
gaschromatography.
The polyunsaturated compounds are more preferably long-chain
polyunsaturated fatty acids of the ω-3 and/or ω-6 series and/or the
pharmaceutically and/or dietetically acceptable derivatives thereof
(including the glycerides containing them); in particular, such long-chain
polyunsaturated fatty acids contain also monounsaturated and/or
saturated compounds.
According to a preferred embodiment, the long-chain
polyunsaturated fatty acids of the ω-3 series -comprised in the
composition with a assay higher than 50% by weight- are selected from
the group consisting of eicosapentaenoic acid (EPA, C20:5 ω-3, all cis)
and/or docosahexaenoic acid (DHA, C22:6 ω-3, all cis) and/or the
pharmaceutically and/or dietetically acceptable derivatives thereof,
whereas the long-chain polyunsaturated fatty acids of the Ω-3 series -
comprised in the composition with a assay lower than 50% by weight- are
selected from the group consisting of C18:3 ω-3 and/or C18:4 ω-3 and/or
C20:4 ω-3 and/or C21:5 Ω-3 and/or C22:5 ω-3 acids, and/or the
pharmaceutically and/or dietetically acceptable derivatives thereof.
The derivatives of the long-chain polyunsaturated fatty acids are
preferably selected from the group consisting of the C1-C3 alkyl esters
and/or glyceric esters and/or the salts thereof with an inorganic or

organic base (sodium, lysine, arginine, choline salts, and the like); the
ethyl esters being most preferred.
According to another preferred embodiment, EPA and/or DHA,
and/or the derivatives thereof are concentrated up to a
gaschromatographic purity higher than 75%, in particular higher than
80%, more preferably higher than 85% and most preferably higher than
90% by weight.
Also variable quantities of ethyl esters of minor ω-3 components, as
described in the above-mentioned monograph of E.P. 2000, as well as ω-6,
monounsaturated and saturated ethyl esters, usually in quantities even
more limited could be present in the composition obtained by carrying out
the process of the invention.
In particular, such composition has a content of oligomeric
impurities (as well as the other by-products of the process) lower than 2%,
more preferably lower than 1.5%, most preferably lower than 1% by
weight, according to the analytic specifications required by each
commercial products.
Foreign impurities, for example those deriving from environmental
pollutants, such as heavy metals, usually measured in concentrations of
"parts per million" (ppm), will always be conform to the analytic
specifications, in particular the ones of E. P. 2000. A typical composition,
obtained by the process of the invention, having an iodine index higher
than 320, will have f. i. an acidity index not higher than 2, peroxide index
not higher than 20, anisidine index not higher than 20; as well as heavy
metals not higher than 10 ppm, Hg and Pb not higher than 1 ppm,
pesticides not higher than 2 ppm.
The ratio of EPA to DHA, and/or the derivatives thereof is preferably
between 2:1 and 1:2, more preferably between 1.5:1 and 0.9:1.
EPA and/or the derivatives thereof are preferably at least 40% by
weight and usually range between 40 and 60% by weight, whereas DHA
and/or the derivatives thereof usually range between 25 and 50% by
weight and are preferably at least 34% by weight.
According to a further preferred embodiment, the EPA and DHA ethyl
esters assay is at least 80% by weight, the EPA ethyl ester assay being at

least 40% by weight and the DHA ethyl ester assay being at least 34% by
weight; the total ω-3 acids ethyl esters assay being at least 90% by weight.
The EPA and DHA ethyl ester assay is preferably higher than 85% by
weight.
A still further preferred embodiment of the process of the invention
provides that minor ω-3 components, with C20, C21, C22 (or also C18)
structure (meaning both acids and/or the derivatives thereof), can be
present in a content higher than 1%, preferably higher than 3% by weight,
as described in IT 1235879, or be in total (C18:3 ω-3, C18:4 ω-3, C20:4
ω-3, C21:5 ω-3, C22:5 ω-3) about 10%, as reported in the already above
mentioned E. P. 2000.
In carrying out the process of the invention, the starting unsaturated
compounds may be concentrated by one- or two- step fractioned
complcxing with urea; further, the resulting concentrated unsaturated
compounds being preferably dissolved in aprotic and/or apolar and/or
poorly polar solvents before being purified, the solvent being selected, in
particular, from the group consisting of n-alkane, iso-alkane or cycle—
alkane. Among the preferred solvents, a C5-C8 alkane such as n-hexane
or cyclo-hexane, can be mentioned.
According to a preferred embodiment, the purification is carried out
by contacting the concentrated unsaturated compounds with the silicon
and/or aluminium derivatives in batch, under stirring; alternatively, the
purification is carried out by percolating the concentrated unsaturated
compounds through the silicon and/or aluminium derivatives.
The purification is carried out preferably at 10-40oC, in particular at
20-25°C, for a time between 5 minutes to 24 hours, in particular for 0.1-4
hours; further, the purification is advantageously carried out in the dark
and in the absence of oxygen.
The silicon and aluminium derivatives preferred for carrying out the
process of the invention have, typically, any granulometry, porosity, grade,
strength and type and are selected from the group consisting of silica gel;
basic, acid or neutral alumina; also their derivatives useful as adsorbents
on the basis of bipolar interactions such as, f. i., the silicate, aluminate,
and silico-aluminate of such derivatives can be mentioned as well; in

particular, the silicon and aluminium derivatives are Florisil® and/or
Chromosorbs® and/or Zeolites®.
According to another preferred embodiment, the process of the
invention comprises, after the purification, concentrating the resulting
unsaturated compounds at a temperature lower than the boiling point of
the solvent and at a pressure lower than 200 mm Hg and then
evaporating to dryness under vacuum or inert gas flow.
Also preferred is including the composition obtained by the process of
the invention in a pharmaceutically and/or dietetically acceptable vehicle
and/or excipient and/or diluent; the composition being preferably in the
form of soft gel capsules.
The composition obtained by carrying out the process of the
invention can be used for the preparation of a pharmaceutical formulation
for the prevention and/or treatment and/or prophylaxis of multiple risk
factors for cardiovascular diseases, such as hypertriglyceridemia,
hypercholesterolemia, and hypertension, and of cardiovascular diseases,
such as arrhythmia and atrial and/or ventricular fibrillation,
decompensation and cardiac insufficiency; for the primary and secondary
prevention of sudden death of cardiac origin and secondary prevention of
re-infarction; for the treatment of every other pathology already known as
being sensitive to the compositions of EPA and/or DHA or their
derivatives, such as autoimmune illnesses, ulcerative cholitis, tumor
pathology, nervous system illnesses, cell aging, cerebral infarct, ischemic
diseases, psoriasis.
As it is known, the composition can be used to prepare
pharmaceutical and/or dietetic formulations suitable for topic, parenteral
or oral use, preferably made of soft gel capsules, and contain 250-1500,
preferably 300-1000 mg of the composition obtained by carrying out the
process of the invention.
Any other known composition comprising unsaturated compounds
having a assay higher than 50%, can be obtained, in the above specified
limits, by the process of the invention which leads to compounds which
can be used for all pharmaceutical and para-pharmaceutical uses
(dietetics, etc.) as described in the prior art.

According to the invention, the raw materials have to show a
minimum content, measured as gaschromatographic purity, higher than
50% and, in general, equal to the assay required for the finished
compound. It will easily be possible to an average man skilled in the art to
prepare such raw materials through methods known in literature. For
example, a composition of EPA and DHA ethyl esters will easily be
obtained through direct transesterification, with ethanol and a catalyst,
preferably an alkaline one, of the triglycerides of certain fish oils (sardine,
mackerel, codfish, salmon oils, etc.; having, for instance, a content of
about 12-18% by weight of EPA and of about 8-12% by weight of DHA),
according to known methods (Lehman LW, Gauglitz EJ jr., Journal Am.
Oil Chem. Soc., 41, 533, 1964).
Starting from such compositions having an overall content of 20-30%
by weight of EPA and DHA ethyl esters, it would be easy for an average
man skilled in the art to obtain compositions with higher concentration,
f.i. higher than 50% by weight, according to methods known in the art (f.
i., Abu-Nasr AM et al., Journal Am. Oil Chem. Soc., 31, 16, 1954), f. i. by
complexing with urea, followed by isolation and discharging of saturated
and monounsaturated components, or by other methods.
In the above mentioned case, by modifying the urea quantities and
other experimental parameters, it is possible to reach compositions of
EPA and DHA ethyl esters, even higher than 50% or even 75, 80, 85, 90%;
all these compositions being useful as raw materials to the purposes of
the process of the invention which, as mentioned above, can be carried
out even in just one step. Anyway, the compositions having a total
concentration of EPA and DHA ethyl esters of 50% by weight, already
available on the market, can be, at their turn, concentrated to 75, 80, 85,
90% by weight or more (particularly, when the minor ω-3 components are
included), as requested, by means of complexing with urea, wasting
saturated and monounsaturated esters, and enrichment of
polyunsaturated esters in a further step of preparation.
It is worth noting that the above reported concentrations represent
the "apparent assays" of the compositions, which actually -if obtained
according to literature procedures, particularly by concentration through

urea complcxing and if not submitted to additional careful phase of
purification- are always undoubtedly contaminated by substantial
quantities of "oligomers" as above defined and by other impurities. As
mentioned above, the presence of oligomers can be occasionally ranged
between 1 and 30%, depending on the process undergone and on the
work accuracy: only their presence as well as the apparent assay higher
than 50%, involve their use as starting unsaturated compounds in both
steps of purification and concentration of the process of the invention.
Oligomers in a relatively low range, between 1 and 2%, can therefore
characterize both the starting and the final unsaturated compounds,
depending on the desired specifications.
In the above mentioned case of compositions based, f. i., on EPA and
DHA ethyl esters, the above starting material may be used as such, in oily
form, or is preferably dissolved in 3-50 volumes, usually 5-20 volumes, of
an aprotic and/or apolar and/or poorly polar solvent, as above mentioned.
According to the process of the invention, the unsaturated
compounds are then preferably contacted and/or percolated on inorganic
substrates as silicon and aluminium derivatives, so inducing a chemo-
physical link with the polar by-products contained, as well as their
isolation and removing.
In other words, the capacity to interact and to link (to bind) polar
derivatives of unsaturated compounds, particularly oxidation polar
derivatives and mainry of oligomeric and polymeric type, with inorganic
substrates -typicalry represented by silicon and aluminium derivatives-
allows to obtain a composition which is unexpectedly free of noxious by-
products.
The process of the invention is therefore deemed to represent an
advantageous substitute of the usual distillation processes, coupled or
not to chromatographic processes.
It is also possible to adopt a so-called "batch process', in this case,
preferably under slow stirring, or more preferably by percolation through
the silicon or aluminium derivative, with a flow speed depending on the
involved volumes, which is not anyway generally critical for the process.
The process of the invention cannot be defined as a 'chromatographic

process', because neither fractioning nor discharging of foreign material is
requested, since the link of polar and/or oligomeric and/or foreign by-
products is strongly selective and specific. In the process of the invention,
the solution contacted with the silicon or aluminium derivative can be
collected as a unique solution, the gaschromatographic composition
remaining substantially unchanged, differently from the distillation
processes. This solution is then preferably evaporated to dryness, at a
temperature Lower than the boiling point of the solvent and at a pressure
lower than 200 mm Hg, according to methods known to the average man
skilled in the art, and any residual solvent is definitely eliminated, mixing
up the oily mass by means of vacuum or inert gas, till a content lower
than the one provided in the adopted specifications or fixed by the
commercial use or by Pharmacopoeias.
The composition thus obtained has then the absolute purity as
requested, it does not need any further purification and can be used as
such for all indications and pharmaceutical and para-pharmaceutical
formulations known in the prior art.
The composition obtained according to the process of the invention,
in particular the composition of EPA and DHA ethyl esters, is therefore
conform to the commercial products obtained by molecular distillation
and to the products already known for pharmaceutical, para-
pharmaceutical, dietetic, alimentary use, etc. as, f. i., the ones described
in EP-B-0292846, EP-B-0409903, IT 1235879, EP-B-1152755, partly
already mentioned, as well as in the mentioned monograph of E. P. 2000.
Therefore, it could be used -for example- in the treatment or the
prevention of multiple risk factors for cardiovascular diseases, as
disclosed in IT 1235879, in the secondary prevention of cardiovascular
events, mortality and sudden death in already infarcted patients, as
described in EP-B-1152755, in the prevention and the treatment of other
cardiac pathologies, as cardiac insufficiency and decompensation, as
reported in EP-A-1365841, as well as in the primary cardiac prevention,
in the arrhythmia and atrial and/or ventricular fibrillation treatment, and
in all other known therapeutic and non-therapeutic indications, (dietetic,
alimentary, etc.).

The following examples illustrate the invention without limiting it.
Example 1
15 grams of urea were dissolved in 150 ml of ethanol at 70°C and
under nitrogen. A 10 g composition of EPA and DHA ethyl esters -
obtained by transesterification with ethanol and NaOH, followed by a
complexing with urea in EtOH/EtOH 95°, according to the disclosure of
EP-B-0255824- having 54.2% purity, and 51.0% assay (GC), was added
under stirring and far from light. The mixture was kept under stirring for
15 minutes and left to cool. After one night, the precipitate was removed
by filtration and the solution was concentrated to a small volume through
distillation under a 50 mm Hg pressure. The residue was treated by
sodium chloride solution and n-hexane extracted. The organic phase,
dried with sodium sulphate and evaporated to dryness, led to a
composition of EPA and DHA ethyl esters, 85.6% purity, 77.3% assay
(GC).
Example 2
5 grams of the composition of EPA and DHA ethyl esters, obtained as
per Example 1, were dissolved in 65 ml of hexane and percolated on 6.5
grams of silica gel. The obtained solution was evaporated to dryness at
60°C and under a 50 mm Hg pressure, working in inert atmosphere far
from light. A composition of EPA and DHA ethyl esters was obtained,
85.4% assay (46.6% EPA, 38.8% DHA, GC), acidity index
index
Example 3
5 grams of a composition of EPA and DHA ethyl esters, 76.5% assay
(GC), were treated as per Example 2, through batch procedure and under
slight stirring.
In the end, a composition of EPA and DHA ethyl esters was obtained,
82.3% assay (GC), 91.6% total assay of ω-3 ethyl esters, according to the
E.P. 2000 specifications.
Example 4
5 grams of the composition used in Example 1, were treated as per
the procedure of Example 3, finally obtaining a composition with a 53.8%
assay (GC).

WE CLAIM:
1. Process for the preparation of a composition comprising long chain
polyunsaturated fatty acids of the ω-3 and/or ω-6 series and/or the
pharmaceutically and/or dietetically acceptable derivatives thereof selected from
C1-C3 alkyI esters and/or the salts thereof with an inorganic or organic base with
an assay higher than 50% by weight, wherein the starting polyunsaturated
compounds are first concentrated up to a gaschromatographic purity
corresponding to the assay required for the final composition and then dissolved
in aprotic and/or apolar and/or poorly polar solvents before being purified by
contact with silicon derivatives.
2. Process as claimed in claim 1, wherein the starting polyunsaturated
compounds have a content of oligomeric impurities lower than 30% by weight,
3. Process as claimed in claim 1 or 2 wherein the stating polyunsaturated
compounds have a content of oligomeric impurities lower than 15% by weight.
4. Process as claimed in any of the previous claims, wherein the long-chain
polyunsaturated compounds contain monounsaturated and/or saturated
compounds.
5. Process as claimed in any of the previous claims, wherein the long-chain
polyunsaturated compounds- comprised in the composition with an assay higher
than 50% by weight are selected from the group consisting of eicosapentaenoic

acid (EPA, C20;5ω-3, all cis) and/or docosahexaenoic acid (DHA, C22:6 ω-3, all
cis) and/or the pharmaceutically and/or dietetically acceptable derivatives thereof
selected from C1-C3 alkyl esters and/or the salts thereof with an inorganic or
organic base, whereas the long-chain polyunsaturated compounds-comprised
in the composition with an assay lower than 50% by weight- are selected from
the group consisting of C18:3 ω-3 and/or C18:4 ω-3 and/or C20:4 ω-3 and/or
C21.5 ω=3 and/or C22:5 ω-3 acids, and/or the pharmaceutically and/or
dietetically acceptable derivatives thereof selected from C1-C3 alkyl esters and/or
the salts thereof with an inorganic or organic base.
6. Process as claimed in any of the previous claims, wherein the C1-C3 alkyl
esters are ethyl esters.
7. Process as claimed in claim 5 or 6, wherein EPA and/or DHA, and/or the C1-C3
alkyl esters and/or the salts thereof with an inorganic or organic base are
concentrated up to a gaschromatographic purity higher than 75% by weight.
8. Process as claimed in any of claims 5-7, wherein EPA and/or DHA, and/or the
C1-C3 alkyl esters and/or the salts thereof with an inorganic or organic base are
concentrated up to a gaschromatographic purity higher than 80% by weight.
9. Process as claimed in any of claims 5-8 wherein EPA and/or DHA, and/or the
C1-C3 alkyl esters and/or the salts thereof with an inorganic or organic base are
concentrated up to a gaschromatographic purity higher than 85% by weight.

10. Process as claimed in any of claims 5-9, wherein EPA and/or DHA, and/or
the C1-C3 alkyl esters and/or the salts thereof with an inorganic or organic base
are concentrated up to a gaschromatographie purity higher than 90% by weight.
11. Process as claimed in any of claims 2-10, wherein the composition has a
content of oligomeric impurities lower than 2% by weight.
12. Process as claimed in any of claims 2-11, wherein the composition has a
content of oligomeric impurities lower than 1.5% by weight.

13. Process as claimed in any of claims 2-12, wherein the composition has a
content of oligomeric impurities lower than 1% by weight.
14. Process as claimed in any of claims 5-13, wherein the ratio of EPA to DHA,
and/or the C1-C3 alkylesters and/or the salts thereof with an inorganic or organic
base is betweedn2:l and 1:2.
15. Process as claimed in any of claims 5-14, wherein the ratio of EPA to DHA,
and/or the C1-C3 alkylesters and/or the salts thereof with an inorganic or organic
base is between 1.5:1 and 0.9:1.
16. Process as claimed in any of claims 6-15, wherein the EPA and DHA ethyl
esters assay is at least 80% by weight, the EPA ethyl ester assay being at least
40% by weight and the DHA ethyl ester assay being at least 34% by weight; the
total ω-3 acids ethyl esters assay being at least 90% by weight.

17. Process as claimed in any of claims 6-16 wherein the EPA and DHA ethyl
ester assay is higher than 85% by weight.
18. Process as claimed in any of claims 5-17 wherein the content of the C20,
C21 and C22 ω-3 acids and/or C1-C3 alky I esters and/or the salts thereof with an
inorganic or organic base is higher than 1% by weight.
19. Process as claimed in any of claims 5-18, wherein the content of the C20,
C21 and C22 ω-3 acids and/or C1-C3 alkyl esters and/or the salts thereof with an
inorganic or organic base is higher than 3% by weight.

20. Process as claimed in any of the previous claims, wherein the starting
polyunsaturated compounds are concentrated by one-step fractioned complexing
with urea.
21. Process as claimed in any one of claims 1-19, wherein the starting
polyunsaturated compounds are concentrated by two-step fractioned complexing
with urea.

22. Process as claimed in any of the previous claims, wherein the solvent is
selected from the group consisting of n-alkane, iso-alkane or cycb-alkane.
23. Process as claimed in any of the previous claims, wherein the solvent is a
C5-C8 alkane,

24. Process as claimed in any of the previous claims, wherein the solvent is n-
hexane or cyclo-hexane.
25. Process as claimed in any of the previous claims, wherein the purification is
carried out by contacting the concentrated polyunsaturated compounds with the
silicon derivatives in bath, under stirring.
26. Process as claimed in any of claims 1-24, wherein the purification is carried
out by percolating the concentrated polyunsaturated compounds through the
silicon derivatives.
27. Process as claimed in any of the previous claims, wherein the purification is
carried out at 10-40°C, for a time between 5 minutes to 24 hours.

28. Process as claimed in any of the previous claims, wherein the purification is
carried out at 20-25°C, for 0.1-4 hours.
29. Process as claimed in any of the previous claims, wherein the purification
is carried out in the dark and in the absence of oxygen.
30. Process as claimed in any of the previous claims, wherein the silicon
derivatives are selected from the group consisting of silica gel; the silicate.
31. Process as claimed in any of the previous claims, wherein the silicon
derivatives are magnesium silicate and silicon dioxide.

32. Process as claimed in any of the previous claims which comprises, after the
purification, concentrating the resulting polyunsaturated compounds at a temperature
lower than the boiling point of the solvent and at a pressure lower than 200 mm Hg and
then evaporating to dryness under vacuum or inert gas flow.
33. Process as claimed in any of the previous claims, wherein said composition is
present in a pharmaceutically and/or dietetically acceptable vehicle and/or excipient
and/or diluent.
34. Process as claimed in any of the previous claims, wherein the composition is in
the form of soft gel capsules.

Process for the preparation of a composition comprising long chain
polyunsaturated fatty acids of the ω-3 and/or ω-6 series and/or the
pharmaceutically and/or dietetically acceptable derivatives thereof selected from
C1-C3 alkyl esters and/or the salts thereof with an inorganic or organic base with
an assay higher than 50% by weight, wherein the starting polyunsaturated
compounds are first concentrated up to a gaschromatographic purity
corresponding to the assay required for the final composition and then dissolved
in aprotic and/or apolar and/or poorly polar solvents before being purified by
contact with silicon derivatives.